In a mobile communications network, there are problems such as areas in which radio waves are heavily attenuated due to blockage of buildings or areas in which radio waves cannot be detected due to distant base stations. In order to solve the problems, standardization of a relay node is discussed in, for example, IEEE 802.16j, IEEE802.16m, LTE-Advanced.
Various types of relay nodes are being considered. The relay nodes can be broadly categorized into two types. The first type is an AF (Amplitude and Forward) type which performs relay while preventing delay by adding an amplitude amplifier. The second type is a DF (Decode and Forward) type which performs relay after decoding data and performing error correction on the decoded data.
FIG. 1 is a schematic diagram illustrating a wireless communications network system 100 according to a related art example. In the wireless communications network system 100, signals transmitted from plural user equipments UE1, UE2 are multiplexed by a relay node RN during uplink (UL) communication and re-transmitted to a base station BS.
FIG. 1 also illustrates the frequency distribution of the signals transmitted by the user equipments UE1, UE2, and the relay node RN, respectively. The user equipments UE1, UE2 transmit signals with a single carrier. The signals transmitted from the user equipments UE1, UE2 are combined (synthesized) with a multicarrier.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-295778    Patent Document 2: Japanese Laid-Open Patent Application No. 2000-31876
When signals are transmitted by the multicarrier, the signals are not transmitted with constant amplitude in a time domain. This leads to a problem of PAPR (Peak to Average Power Ratio). As a result, wireless usage efficiency is degraded.